1. Field of the Invention
The invention relates to portable thermal rescue systems designed to rapidly raise or rapidly lower and thereafter to control the body temperature of a mammal, particularly a human (or person) by thermal exchange between a liquid and the mammal via direct liquid-to-skin contact. The invention allows topical delivery of medicines to the mammal and is particularly apt for immediate treatment in the field of bum injuries, hypothermia, strokes, infarctions, heart attacks. Head injuries and other trauma where prompt temperature control a mammal""s body is of therapeutic or medical value. The present invention generally relates to a water-proof mummy bag and related system for cooling and/or heating a mammal, particularly a human (or person) via thermal exchange with a liquid. The present invention is particularly apt for emergency, rapid treatment and also in situ emergency treatment for mammals suffering from hypothermia, exposure, strokes, heart attacks, infarctions, head injuries and other trauma.
2. Background Art
In medical emergencies where a mammal""s body temperature is critical, techniques for raising or lowering a mammal""s body temperature in a timely manner are limited by current technologies and means. The prior art, whether blankets, electric blankets, warming coats, hot water containers, heating pads or similar devices all transfer heat into a human (or other mammal) suffering hypothermia using an air medium and are limited by the low transfer rate of heat from air into the body through skin tissues. To increase heat transfer rates to an inanimate object, the temperature of the medium is simply increased. However, where the object is a mammal the temperature of the medium is limited to what the skin of the mammal can tolerate without bum damage. Since increasing the temperature of the air medium is limited, the rate of heat transfer is limited. Once the maximum tolerable air temperature has been reached increasing the rate of circulation of the air is the only way to increase the rate of transfer of heat to or from a mammal body. Sufficient air circulation is not practical or possible to reach the desired heat transfer rates. Since human skin (and most mammal skin) cannot tolerate the high temperatures of air that are required to achieve the heat transfer rates that are often required, it is often impossible to save the mammal""s life. This result is due to the combination of three factors: first; the low heat capacity of medium of heat transferxe2x80x94air, second, limitations on circulation of air and third, the low temperature tolerance for the skin of humans and mammals.
However, a liquid heat transfer medium such as water or other aqueous liquid uses the far more powerful heat transfer rates of conduction from liquid to the body of a mammal. This liquid-to-body heat transfer rate is four to five times that of the air-to-body heat transfer rate at the same temperature due in large part to the much higher heat capacity of aqueous liquids compared the heat capacity of air. As with air, circulating the liquid medium around the body increases the heat transfer rate.
Since both air and water heat transfer mechanisms operate through the skin, clothing inhibits the heat transfer from air and must be removed for optimal recovery of body temperature by air heat transfer. With a direct liquid heat transfer medium, removal of clothing, especially wet clothing, is not as critical, can be avoided and in bum cases, it is often is undesirable or impossible without harmful side effects. In these circumstances the mammal is placed directly in the liquid suspending the mammal, allowing the mammal""s coverings or clothes to float free, rather than clinging to the body as in an attempted recovery of body temperature by air heat transfer. The far higher heat capacities and heat transfer rates of liquids combined with circulating the liquid makes this possible.
Human skin can easily tolerate without undesirable side effects, water temperatures of up to 110 degrees F. for extended periods of time as is frequently demonstrated by therapeutic and recreational users of hot tubs. For some mammals, higher temperatures may be tolerated. The ability of human and other mammal tissue to tolerate beyond a brief period, heat transfer rates from conduction due to temperature differences more than 12 degrees F. above normal body temperature, approximately 110 degrees F., is not knownxe2x80x94and will not be until a mammal whose hypothermia is so extreme that their skin temperature is substantially below the normal 98.6 degrees F. and the thermal rescue system is put to work to save the mammal""s life. Humans regularly wash and shower using water temperatures as high as 120 degrees F. In extreme hypothermia cases, a mammal""s body temperature may be as low as 70 degrees F.xe2x80x94the minimum body temperature from which mammals frequently manage to recover from hypothermia. Some indication of local tolerances can come from frostbite recovery efforts, but a whole body experience is not known at this time.
Since the possible side effects for hypothermia mammals of heat transfer rates higher than those generated by 12-to 15 degree F. temperature differences have not yet been established, it is an important feature of the Portable Thermal Rescue/Recovery System that the temperature can be adjusted to the maximum ability and condition of each particular mammal to handle the rate of recovery.
In lowering body temperature, the bodies of mammals are able to withstand heat transfer rates resulting from immersion in liquids 40-50 degrees F. colder than normal body temperature. Since the body temperature of a mammal suffering from a trauma needing reduced body temperature need be lowered only 10 degrees F. to realize the therapeutic benefits, the liquid medium may not have to be cooled below ambient room temperatures of 70-75 degrees F. Where additional or more rapid cooling is needed, the circulation of the liquid by the pump can be added, increased or the water replaced.
When a mammal is suffering from hypothermia, whether from a marine accident or MOB (man overboard) incident ice collapse, circulatory infarction or other medical emergency or event causing exposure to the elements, the best first aid is to restore the body temperature of the mammal as quickly as possible without inducing secondary effects.
When a mammal has been burned, the best first aid is to place the burned areas in cool preferably oxygenated water as soon as possible. This cool water reduces scarring and further damage caused by the effect of excessive heat on human and animal tissues. Reducing the temperature by immersion in cool water has these benefits: first, it slows or stops continuing bum damage; second, it reduces the need of the skin tissue for oxygen; and third, it provides a source of supplemental oxygen to the burned tissues.
Where the area of the burn is large or covers a significant portion of the body so that local topical temperature relief of an ice-pack or a series of ice packs is not practical, possible or available, a thermal rescue/recovery system provides the best quickest means of providing first aid to both alleviate pain and limit further damage. In addition immersion in the liquid of the thermal rescue/recovery system promotes healing by eliminating or minimizing the need for damaged portions of the skin to support the weight of the mammal allowing all surface areas of the mammal to receive relief at the same time. This is especially valuable where bums cover sufficiently large portions of the body that some burned tissue has to support the weight of the body.
Medical research shows strokes typically occur when a blood clot lodges in the tree of arteries in the head, choking off the flow of blood. Quickly giving a clot dissolver can forestall much of the damage, but most mammals do not receive medical care or reach a hospital soon enough for the diagnosis, prescription and administration of a prescribed medicine before much of the irreversible damage from trauma has occurred. After an initial stroke, brain cells begin to die immediately and continue to die for several more hours, killed by a chemical chain reactions triggered by proteins that ooze from neighboring damaged cells. Research shows quickly cooling the brain will slow and prevent much of this damage by slowing these metabolic processes. Since brain cells are continuing to die following a stroke, lowering the stroke victim""s body temperature lowers the temperature of the blood flowing to the victims brain, thereby lowering the temperature of the brain. Lowering body temperature immediately where the victim is located may in many cases be more important use of time than transport to a medical care or a hospital. Once thermal control has been initiated: the victim should be transported to medical care of a hospital as soon as possible. Even in an EMS vehicle, before the victim gets to medical care or to the hospital lowering body temperature has a prophylactic effect as this lowers the temperature of the brain, slowing, arresting, diminishing and/or mitigating subsequent consequential damages caused by the initial blood lot. Similar results are indicated for heart attack victims where a clot has landed in the heart and other infarctions such as those occurring in the spleen, liver and other vital organs. The portable thermal rescue/recovery system provides this immediate life-saving temperature reduction for a wide variety of medical emergencies.
The present invention, the portable thermal rescue/recovery system (PTRRS), can be used as first aid for victims of hypothermia, stroke, heart attack, infraction, burns and other medical conditions body temperature control is needed. This system is suitable for use in land, sea and air rescue vehicles including Emergency Medical Service (EMS) vehicles which are used to recover and/or transport mammals, primarily humans, needing body temperature control. The volume of liquid needed for the PTRRS is xc2xd to xc2xe of the weight of the mammalxe2x80x94or in the case of a human, not more than 100-150 lbs. Hence, the PORTABLE THERMAL RESCUE/RECOVERY SYSTEM is suitable for Coast Guard, Navy, law enforcement and other rescue helicopters and aircraft as well as land and water based rescue craft and vehicles of all sizes and in a personally portable mode, is suitable where the mammal cannot be quickly be moved to the rescue vehicle and immediate, in situ temperature control is indicated.